Sprint’s move toward network prioritization, specifically slowing connection speeds for the top five percent of data users on congested sites, seems a lot like throttling.

But the network, which touts an “Unlimited for Life” guarantee, said the practice differs from throttling. A Sprint spokesperson defined throttling as, once a subscriber exceeds a data cap, speeds are slowed for the remainder of the billing period, regardless of location or network conditions.

“With network prioritization, speed is reduced only when a customer is connected to a congested cell site, during a time of congestion. Once the customer connects to a non-congested site, or the congested site becomes no longer congested, speed returns to normal,” a Sprint spokesperson told Wireless Week. “This means any impact to a customer’s data experience may last as little as a matter of seconds or hours, depending on their location and time of day.”

Sprint confirmed that network prioritization would be impacting all postpaid and prepaid customers—on Boost and Virgin Mobile—beginning with June data usage, adding that the hope is that the “majority of our customers will be positively impacted with a better network experience.”

Sprint doesn’t provide an exact amount of data use that will put a user in the network prioritization zone, but Sprint says that subscribers who use more than 5GB monthly are more likely to fall into the five percent.

The carrier doesn’t explain how it determines when a cell site is congested, only that a “fairness algorithm” is used to “ensure no one user is deprived of network resources.”

In March, Sprint announced that in May Boost and Virgin customers who exceed their data limits would begin experiencing slower throttling speeds.

“This change comes about because of the enormous data usage driven by the increasingly sophisticated smartphones we make available, and the more extensive uses customers are finding for these devices,” a Sprint spokesperson said in a statement. “We want to be able to serve customers who use our unlimited plans for their daily activity.”